Due to magnetic properties, ferromagnetic particles (nanoparticles) are recently used as active pharmaceutical ingredients for a magnetic resonance imaging method (MRI), a drug delivery system (DDS), a local hyperthermia treatment and so on.
JP2006-28032A discloses a method of generating magnetite particles, which are one type of such ferromagnetic particles, by using a coprecipitation reaction. Specifically in this method, a predetermined amount of ferrous chloride (FeCl2) solution and a predetermined amount of ferric chloride (FeCl3) solution are put into a reaction container. While the solutions are heated and stirred in the reaction container, sodium hydroxide (NaOH) solution is added thereto. Thus, a coprecipitation reaction between ferrous ions (Fe2+) and ferric ions (Fe3+) occurs so that magnetite (Fe3O4) particles are generated.
In such a conventional method, when magnetite particles are industrially produced in large volume, a great amount of reaction liquid is stirred in a reaction container. In this case, the reaction liquid is likely to vary in temperature and a mixed condition of the reaction liquid is likely to be non-uniform, which makes it difficult to improve generation efficiency of magnetite particles. There is another problem in that the thus generated magnetite particles tend to vary widely in composition and dimension.
In addition, in the manufacture of active pharmaceutical ingredients, regulations related to production control and quality control on medical drugs and medical devices, i.e., the GMP (Good Manufacturing Practice) must be observed in general. To be specific, for example, a reaction liquid is required to be maintained in an aseptic condition without being reacted with an outside air. However, in the conventional method in which a reaction liquid is stirred in a reaction container, it is difficult to comply with the GMP.